Britain’s competition watchdog has fined Pfizer a record £84.2 million for its role in ramping up the cost of an epilepsy drug by as much as 2,600 per cent.

The Competition and Markets Authority (CMA) also fined Flynn Pharma £5.2 million for overcharging for phenytoin sodium capsules, following a dramatic price hike in 2012.

The CMA’s ruling comes amid a growing debate on both sides of the Atlantic about the ethics of price hikes for old off-patent medicines that are only made by a few firms and where there is little competition.

US drugmaker Turing Pharmaceuticals caused outrage last year by raising the US price of Daraprim, an old anti-infective drug, by more than 5,000 per cent to $750 a pill.

In the case of phenytoin sodium capsules, the UK price charged for 100 mg packs of the drug jumped from £2.83 to £67.50 in 2012, before reducing to £54 from May 2014.

As a result, annual spending on the capsules by Britain’s National Health Service rose from £2 million in 2012 to about £50 million in 2013. The CMA said UK prices were many times higher than elsewhere in Europe.

Pfizer used to market the medicine under the brand name Epanutin but sold the rights to Flynn, a privately owned British company, in September 2012.